The US says it will support providing advanced fighter jets including US-made F-16s to Ukraine and also back training Ukrainian pilots to fly them.
A senior White House official said President Biden had told G7 leaders in Japan of the decision.
President Volodomyr Zelensky, who has requested fighter jets for months, said the decision would “greatly enhance our army in the sky”.
US approval for the scheme means other nations can export their F-16s.
This is because the US legally has to approve the re-export of equipment purchased by allies.
The US would “support a joint effort with our allies and partners to train Ukrainian pilots on fourth-generation fighter aircraft, including F-16s, to further strengthen and improve the capabilities of the Ukrainian Air Force”, the official said.
“As the training takes place over the coming months, our coalition of countries participating in this effort will decide when to actually provide jets, how many we will provide, and who will provide them.”
Ukraine has repeatedly lobbied its Western allies to provide jets to help in its fight against Russia and Mr Zelensky welcomed what he described as a “historic decision”, adding that he looked forward to “discussing the practical implementation” of the plan at the G7 summit in Hiroshima, where he is expected to appear.
“This will greatly enhance our army in the sky,” he tweeted.
The US had been sceptical about providing Ukraine with modern fighter jets – at least in the near term. Its focus has instead been on providing military support on land.
Senior US military officials who’ve spoken to the BBC in the past have questioned whether Western-supplied fighter jets will dramatically alter the conflict, with Russia’s large air force still struggling to gain air superiority and the high density of air defence systems on the ground.
So this change in US policy is significant. However, training pilots to fly F-16 jets will take time. Ukraine does have more trained fighter pilots than aircraft at present. But even training experienced fighter pilots on a new plane could take up to four months for an already experienced pilot.
And then nations will need to agree to supply the jets. The F-16 is widely used by a number of European and Middle East nations as well as the US, which still manufactures the aircraft. Who is willing to supply the jets is the next key question.
The UK, Netherlands, Belgium and Denmark also welcomed the US move.
UK Prime Minister Rishi Sunak tweeted: “The UK will work together with the USA and the Netherlands, Belgium and Denmark to get Ukraine the combat air capability it needs.”
The UK does not have any F-16s in its air force itself.
Denmark has announced it too will now be able to support the training of pilots, but did not confirm whether it would send any jets to Ukraine. Denmark’s air force has 40 F-16s, around 30 of which are operational.
Earlier this week, Mr Sunak and Dutch Prime Minister Mark Rutte said they would build an “international coalition” to provide fighter jet support for Ukraine.
Mr Sunak said the UK would set up a flight school to train Ukrainian pilots. French leader Emmanuel Macron said his country was willing to do the same but would not provide jets.
Some of the opposition to sending the jets has centred around maintenance issues, with former Nato official Dr Jamie Shea saying they require extensive maintenance after almost every fight.
Some Nato member countries have also expressed their worries that handing jets to Ukraine would be viewed as escalating the war, risking a direct confrontation with Russia.
At the start of Russia’s full-scale invasion, Ukraine was believed to have around 120 combat capable aircraft – mainly consisting of aging Soviet-era MiG-29s and Su-27s.
But officials say they need up to 200 jets to match Moscow’s air-power – which is thought to be five or six times greater than Kyiv’s.
Mr Zelensky has primarily been asking its allies for F-16s. First built in the 1970s, the jet can travel at twice the speed of sound and can engage targets in the air or on the ground.
While now eclipsed by the more modern F-35, it remains widely in use. Experts say modern fighters like the F-16 would help Ukraine strike behind Russian lines.
Earlier this year some Eastern European countries sent Soviet-era Mig fighter jets to Ukraine.